1. Field of the Invention
The present invention relates to a digital television (TV) broadcast signal receiver that can receive digital television broadcast signals such as ATSC (Advanced television systems Committee).
2. Description of the Related Art
In the North American Continent where an ATSC digital television broadcast (it is abbreviated to a hereinafter digital TV broadcast) is performed, plains are dotted with metropolises, so that various digital TV broadcast signals broadcasted in the suburbs of each metropolis can be received at other cities or the halfway point of the cities. In consideration from a user who receives the TV broadcast signals, since many TV broadcast signals are transmitted in various directions, it is necessary to regulate a direction of an antenna in an orientation to a TV broadcasting station from which a program which he wants to watch is delivered. Therefore, a multi-directional antenna such as a smart antenna is put into practical use.
With respect to an apparatus connected to a multi-directional antenna such as a smart antenna, there are prior arts of Japanese Laid-Open Patent Publications No. 2003-224502, 2003-60423 and 2002-76742.
According to the EIA-909 technical standard, it is provided that a smart antenna has sixteen signal receiving directions in respective directions where a circle is divided into sixteen. A digital TV broadcast signal receiver in compliance with the EIA-909 technical standard can adjust an effective signal receiving direction of the multi-directional antenna such as the smart antenna in all sixteen signal receiving directions. Generally, in the digital TV broadcast signal receiver, TV broadcast signal are previously received in each of sixteen signal receiving direction of a multi-directional antenna with respect to each of normally receivable channel, an intensity of each received TV broadcast signal is measured, and a direction showing the largest value of the sensitivity is defined as an optimum signal receiving direction of each channel.
In general, an antenna of a TV station, that is, a position of a TV tower is invariance. Thus, the optimum signal receiving direction of each channel is once decided, it is no need to reset the optimum signal receiving direction. For example, in the United States, a TV station can be established relatively easier. In contrast, a TV station suddenly becomes bankrupt. Therefore, it happens that a new channel, which cannot be received beforetime, can be received, or an old channel receivable long before cannot be received. Furthermore, a signal receiving condition of a TV broadcast signal of a channel is varied due to construction of a high-rise building. Thus, a TV broadcast signal cannot be received normally suddenly in a direction, in which the TV broadcast signal was normally received. In such a case, it wastes time in searching of an optimum signal receiving direction of each receivable channel in all sixteen signal receiving directions, similar to when a multi-directional antenna is newly connected to the digital TV broadcast signal receiver, and it causes the irritation of a user.